Seasonal shifts of the microbial community structure in a winery waste-impacted wetland soil

Abstract

ABSTRACT Wetlands have been identified as viable systems for treating agroindustrial and other effluents. However, the microbial contribution to the bioremediation processes in wetlands is poorly understood. We have investigated the diversity and dynamics of microbial communities in a natural wetland system used to bioremediate winery waste in the Western Cape region, South Africa. Denaturing gradient gel electrophoresis (DGGE) profiles of 16S rRNA gene fragments amplified from surface wetland soil samples (0–5 cm depth) collected between February 2005 and February 2006 indicated that major qualitative and quantitative changes occurred in the structure of the bacterial, total archaeal and methanogenic communities over the course of the year. Conversely, no significant differences were detected in samples recovered over the same period at ca. 25 cm depth. The DGGE patterns from surface samples grouped into two distinct seasonal clusters, which correlated well with considerable differences in effluent chemistry and hence may be related to harvesting activities at the wine estate. The analysis of temporal intensity variations of specific DGGE bands, which reflect the population dynamics of the respective phylotypes, was used to identify taxa potentially involved in the degradation of winery waste compounds. We propose that this is a valid approach to the identification of dominant and temporally responsive microorganisms in passive bioremediation studies.